The present invention relates to a positioning device for positioning an elongated member in an inaccessible space. In particular, the present invention relates to an improved anchor assembly of the type generally described in U.S. Pat. No. 4,075,924 issued to Thomas McSherry et al. on Feb. 28, 1978 and improvements described in U.S. Pat. No. 4,294,156 issued to Thomas McSherry et al. on Oct. 13, 1981. The '924 patent describes an anchor assembly comprising a pair of elongated leg members of flexible material and an elongated anchor member coupled to adjacent end portions of the legs. In the '924 patent the leg members may include resilient means such as traversely bent end portions to resiliently bias the anchor member generally traversely to the legs. In the '156 patent the anchor is hingeably attached to the legs such that the legs can rotate in a plane defined by their longitudinal axis. The hinge effect is accomplished by use of transverse studs at the ends of the legs which engage paired apertures in longitudinal flanges of the anchor member.
In use, both assemblies have their flexible legs bent such that the long dimension of the anchor member is oriented generally parallel to such legs, thereby enabling insertion of the assembly into a hole cut or drilled in a wall or ceiling. In the '924 assembly, the transversely bent end portions of the legs bias the anchor back into its transverse position once it is inserted through the wall far enough to clear the restriction of the hole to this movement. In the '156 assembly the anchor is biased to the transverse position by the resiliency of the legs. In both patents, when the anchor is in the proper orientation for insertion, one leg of the assembly is bowed out away from the other. This bowing is caused by the shorter distance from one aperture to the opposite connection of the leg ends than the distance from the aperture of the straight leg's connection to the opposite connection of the leg ends. After full insertion this bowing creates the spring force that is necessary to bias the anchor member to its transverse position.
Another form of anchor assembly is described in U.S. Pat. No. 4,043,245 issued to Stanley Kaplan on Aug. 23, 1977. In the Kaplan assembly the legs are spaced apart across the narrow dimension of the anchor member and each leg is attached to only one side of the anchor member channel, via a trunnion inserted into an apertured flange.
The '924, '156 and '245 configurations of anchor assemblies have characteristics that can greatly limit the maximum strength of the leg portions and the size of the device as a whole. The legs in the '245 patent are connected with trunnions to the anchor member for relative pivotal movement, but the more secure this connection, the greater potential there is for frictional interference with such pivotal movement. The presence of a resilient biasing means in the '924 patent tends to limit the maximum strength available in the legs of the device. In both '924 and the '156 patents, the presence of the bowed leg during insertion into an opening interferes with the insertion of the anchor assembly and its proper placement.